Although HIV transmission in China has been largely concentrated among injection drug users, commercial sex workers, and former blood plasma donors, the Chinese Government now also considers men who have sex with men (MSM) to be a high-risk group. The latest statistics show that MSM account for 7% of all HIV/AIDS cases in China. A growing number of studies document high-risk behaviors such as unprotected anal intercourse among MSM. Choi and colleagues, for example, found an HIV prevalence rate of 3.1% (based on HIV testing) among Beijing MSM, with a majority of the sample practicing high-risk behaviors such as unprotected anal intercourse. Considering that many Chinese MSM are also married, these findings are especially alarming. In addition, there is a subpopulation of MSM who engage in transactional sex, known locally as "money boys." Research reveals that virtually all of money boys are migrants. Various studies have found that relative to non-migrants, migrants are at greater risk of contracting and transmitting HIV. Given the emergence of MSM (including money boys as a subpopulation) as a high-risk group for the spread for HIV, the proposed 5-year study is to: (1) establish the prevalence of HIV and three sexually transmitted infections -gonorrhea, herpes simplex II, and syphilis - among MSM in Shanghai;(2) examine and describe HIV risks (including sexual risks and substance use/abuse) among non-money-boy MSM and money-boy MSM;(3) examine and describe the willingness to test for HIV and STIs among these two types of MSM;and (4) examine and describe the utility of three recruitment approaches - (a) community popular opinion leader;(b) venue-based approaches;and (c) respondent-driven sampling - in studying HIV-related risks among these two types of MSM. In addition to a systematic investigation of HIV risks among MSM in China, the proposed study also tests the heuristic value of a conceptual model on HIV risks among a high-risk MSM subpopulation, namely the Chinese money boys. Lessons learned have implications for other developing countries such as India, which is experiencing a growing HIV epidemic and has a large, underground MSM population.